This article sets forth a minimum necessary condition for sustainability: the maintenance of the total natural capital stock at or above the current level. This condition embodies a precautionary principle: given the extent to which natural capital has already been damaged or depleted, it would be too risky to allow its significant further loss. Methodological issues raised by this basic condition undifferentiating between growth and development, and the shortcomings of the current macroeconomic measures such as the Gross National Product. Technological issues include the degree to which technical progress can overcome resource constraints on growth. While there are wide disagreements on these issues, this article suggests that a prudent policy for sustainable development must avoid natural capital depletion.
